The use of balloon catheters for dilating or otherwise opening vascular or other body conduits and passageways which have been partially or entirely blocked by deposits or other obstructions is generally known. These prior art balloon catheters generally include an elongate shaft having at least one inflatable and deflatable balloon or sleeve disposed on the leading or distal end. The balloon catheter is introduced into the affected blood vessel or other body passageway and the deflated balloon is maneuvered into the blocked or otherwise obstructed flow path. Once positioned, the balloon is inflated to enlarge the passageway and compress the deposits or obstructions against the inner wall of the vessel.
In addition to the physical enlargement of the flow passageway by mechanical displacement of deposits, modem techniques may include the use of therapeutic medicines and agents to treat the obstructed regions. These drugs are typically used to soften, dissolve or even prevent the reoccurrence of the obstruction. As a specific example, it is well known to treat coronary and peripheral blood vessel obstructions caused by the buildup of fibrin, thrombus or plaque by delivering concentrated doses of agents or medications for direct deposition into the lesion and/or vessel wall.
In a typical procedure involving the application of therapeutic agents using a balloon catheter, the catheter, which includes a series of treatment fluid exit holes, is inserted into the obstructed vessel. Once positioned, relatively large amounts of medication are delivered to the lesion site to "dissolve" and "break up" the obstruction while the catheter is slowly advanced, sometimes over the course of several hours. Since the agents can freely mix with the blood or other fluid in the passageway, increased concentrations of the agent may be required to maintain adequate treatment at the constriction. This can increase costs due to the quantity of drug used, plus the extended use of the physician and the laboratory facilities. In addition the entire vascular system or other passageway may be exposed to the agent, causing serious side effects.
Double balloon catheters have been developed in an effort to temporarily isolate the drug at the site of the lesion. These catheters typically feature two inflatable balloons spaced apart along the distal end of the catheter shaft. Between the balloons is located a plurality of exit ports for infusion of the therapeutic agent. In use, the double balloon is advanced within the vascular conduit so that the two balloons span the lesion site and drug is infused while the balloons are inflated. However, this tends to block all circulating blood flow through the vessel during the administration of the drug.
Double balloon catheters have been proposed to combine, in a single device, the ability to perform angioplasty and to deliver drugs to the angioplasty site without first having to remove the catheter. These devices present the potential for reducing the procedure time and cost of the procedure when combination angioplasty and local drug treatment is planned. However, many of the devices are quite complex and intricate, and thus costly to produce.
Further, some dual purpose angioplasty and drug delivery catheters require repositioning of the catheter after the angioplasty procedure in order to properly deliver the drug to the expanded area of the vessel wall. However, speed and accuracy of treatment are highly important in these angioplasty and drug treatment procedures. Thus, there is a need for a combination angioplasty and drug delivery catheter of a less complex design which does not have to be repositioned between the steps of angioplasty of the lesion site and drug delivery to the site.
Another disadvantage of prior art double balloon angioplasty and drug infusion catheters is their limited ability to operate within smaller vessels and conduits. Since these catheters include an elongate shaft or catheter body which contains three or more longitudinal lumens, their overall outer diameters are typically large.
In addition, each of the lumens typically requires a maximum cross-section to maximize their fluid capacity. However, this tends to further enlarge the overall diameter of the catheter shaft. Attempts to minimize this shaft diameter have previously let to concerns about the strength of the shaft. Thus, there is a need for a catheter shaft having enlarged longitudinal lumens within a relatively small diameter shaft. There is also a need for such a catheter device which is capable of safely operating within smaller vessels and passageways.
Yet another disadvantage of the present balloon catheter devices is their limited ability to efficiently transport body fluid and particularly bypass blood flow around the area being treated. Typically, the drug delivery catheter creates a partial occlusion of the passageway which, when combined with the low volume or slower delivery of the therapeutic drugs due to the smaller lumens, reduces their usability during longer drug delivery procedures. This is particularly disadvantageous where the viability of down stream tissue may be affected by long occlusion times. And, catheter devices which are capable of autoperfusion (bypass of blood flow through the catheter's internal structure) have increased catheter body diameters due to the additional or larger required lumens, or parts therein. This larger catheter device is restrictive when attempting to access narrow or highly occluded passageways as well as remote vascular locations. Thus, there is a need for a balloon catheter which allows efficient autoperfusion without substantially increasing the diameter of the deflated catheter device.
Yet another disadvantage of the present balloon catheter devices is their even larger diameter around each of the attached balloons. Presently, where the balloons are attached to the catheter device, the overall catheter diameter is enlarged, making operation within the smaller passageways commonly found in modern angioplasty procedures problematic. Merely reducing the catheter shaft diameter in the area of the attached balloons may reduce the diameter of the internal fluid delivery lumen and further restrict drug delivery and balloon inflation/deflation times. Thus, there is a need for a catheter device capable of insertion and operation within smaller body passageways and also capable of adequate drug volume delivery between the balloons.